South American bishop going to spa for day of relaxation (7)
I believe the answer is:
sabbath
'day of relaxation' is the definition.
(day of relaxation in some religions)
'south american bishop going to spa' is the wordplay.
'south american' becomes 'SA'.
'bishop' becomes 'B' (chess abbreviation).
'going to' is a charade indicator (letters next to each other).
'spa' becomes 'bath'.
'sa'+'b'+'bath'='SABBATH'
'for' acts as a link.
(Other definitions for sabbath that I've seen before include "Sacred day of the week" , "Day of rest and worship" , "Religious day of rest for Jews and Christians" , "Traditional holy day" , "Period of rest" .)